Zoomed images unexplained panning

Hi all,
I've run into a bizarre issue on my new iMac, running LR Classic 11.31. In Library or Develop module, when I zoom an image in loupe mode, it begins to very slowly pan from right to left, as long as my cursor is hovering over the image area. As soon as I move my cursor away (say, over a side panel) the panning stops. It's as if I was slowly dragging the cursor to pan the image, except the mouse is stationary.

Also, if I hover over the filmstrip in Library module, it starts panning slowly towards the first image in the filmstrip row (ie. from right to left).

This started happening without warning overnight, and I hadn't changed any settings.

To try to solve this I have:

1.  Uninstalled and reinstalled LR Classic without resetting preferences
2.  Uninstalled and reinstalled LR Classic, resetting preferences
3.  Uninstalled v11.31 and installed the previous version 11.3
4.  Rebooted my Mac several times
5. Deleted the plist, rebooted and reset preferences
6. In case it was actually a mouse issue I have changed mice

None of these steps have made any difference. It's as if LR thinks I'm scrolling across the image, or across the filmstrip, when I'm actually doing nothing.

I'm at my wit's end. Any thoughts?

In case it helps, here is my system info:

Lightroom Classic version: 11.3 [ 202204051513-7a25c809 ]
License: Creative Cloud
Language setting: en-GB
Operating system: Mac OS 12
Version: 12.3.1 [21E258]
Application architecture: x64
Logical processor count: 20
Processor speed: 3.6GHz
SqLite Version: 3.36.0
Built-in memory: 65,536.0 MB
Real memory available to Lightroom: 65,536.0 MB
Real memory used by Lightroom: 6,025.2 MB (9.1%)
Virtual memory used by Lightroom: 46,960.6 MB
Memory cache size: 398.2MB
Internal Camera Raw version: 14.3 [ 1072 ]
Maximum thread count used by Camera Raw: 5
Camera Raw SIMD optimization: SSE2,AVX,AVX2
Camera Raw virtual memory: 787MB / 32767MB (2%)
Camera Raw real memory: 851MB / 65536MB (1%)
Displays: 1) 5120x2880, 2) 2560x1440

Graphics Processor Info:
Metal: AMD Radeon Pro 5700 XT

Application folder: /Applications/Adobe Lightroom Classic
Library Path: /Users/David/Pictures/Lightroom/Lightroom-v11.lrcat
Settings Folder: /Users/David/Library/Application Support/Adobe/Lightroom

Installed Plugins:
1) AdobeStock
2) Aperture/iPhoto Importer Plug-in
3) DxO PureRAW 2
4) DxO PureRAW 2 Importer
5) Facebook
6) Flickr
7) Nikon Tether Plugin
😎 ON1 Effects 10
9) ON1 Photo 10
10) ON1 Photo RAW 2022

Config.lua flags: None